1. Field of the Invention
The instant disclosure relates to a method for manufacturing a reflective optical film, and more particularly, to a method for manufacturing a reflective optical film having a thickness gradient variation.
2. Description of Related Art
Polymeric optical films are used in a wide variety of applications such as reflective polarizers. Such reflective polarizer films are used, for example, in conjunction with backlights in liquid crystal displays. A reflective polarizing film can be placed between the user and the backlight to recycle polarized light that would be otherwise absorbed, and thereby increasing brightness. These polymeric optical films often have high reflectivity, while being lightweight and resistant to breakage. Thus, the films are suited for use as reflectors and polarizers in compact electronic displays, such as liquid crystal displays (LCDs) placed in mobile telephones, personal data assistants, portable computers, desktop monitors, and televisions, for example. In commercial processes, optical films made from polymeric materials or blends of materials are typically extruded from a die using a feedblock or cast from solvent. The extruded or cast film is then stretched to create and/or enhance birefringence in at least some of the materials. The materials and the stretching protocol may be selected to produce an optical film such as a reflective optical film, for example, a reflective polarizer or a mirror.